The present invention pertains to the electrical signal generation art and, more particularly, to a means for generating a composite electrical signal.
Whereas composite signal generators, i.e. generators capable of combining two waveforms into one, have been used extensively in the electronics art, there are numerous applications for which existing composite signal generators are inadequate. An example of this inadequacy is the electrical component test art, more particularly, test equipment for checking the lightning protectors of commercial aircraft. Here, a set of lightning protectors are connected between ground and each of three output bus lines from an outboard main generator. The lightning protectors function to prevent equipment damage due to induced transients caused by lightning. Normally, the high induced voltages are grounded through the protectors. However, sustained or excessively high transient voltages may damage the protectors. It is important to proper operation of the aircraft, therefore, that these protectors be checked periodically to insure that they operate at the desired value.
Prior to the instant invention, a very cumbersome and time consuming technique was used for checking such protectors. Its procedure included the operator disconnecting the protector from the bus, connecting it to a a variable alternating current source and monitoring with an AC voltmeter and an oscilloscope. The operator slowly increases the AC voltage on the protector until the oscilloscope waveform indicates that it has activated. The voltage at which this occurred is then compared against a specification.
There has been a long felt need in this art, therefore, for a composite signal generator which can quickly and efficiently test lightning protectors without the need for elaborate test equipment.